Simplify the following expression: $k = \dfrac{60y + 20z}{10z - 60y} - \dfrac{10z}{10z - 60y}$ You can assume $x,y,z \neq 0$.
Since the expressions have the same denominator we simply combine the numerators: $k = \dfrac{60y + 20z - (10z)}{10z - 60y}$ $k = \dfrac{60y + 10z}{10z - 60y}$ The numerator and denominator have a common factor of $10$, so we can simplify $k = \dfrac{6y + z}{z - 6y}$